This is the first study in human subjects with epilepsy of a potential new antiepileptic drug, SB204269. This drug appears to have a unique mechanism of action different from currently known antiseizure drugs. It appears to bind to a unique receptor in the brain, and may affect potassium channels. Animal studies have demonstrated a remarkable lack of neurotoxicity, and good efficacy in several seizure models. This is a Phase I study to determine the adverse effect profile and pharmacokinetics, using a gradually rising dose over 21 days in patients with epilepsy.